1. Field of the Invention
The present invention relates to an illumination apparatus which evenly illuminates an illumination target.
2. Description of the Related Art
Recently, a fiber light source having a small solid-state light source and an optical fiber has been developed. This fiber light source is combined with an imaging unit. This fiber light source is used as an illumination apparatus which emits light from the distal end portion of an elongated structure. This fiber light source is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2009-3228. Jpn. Pat. Appln. KOKAI Publication No. 2009-3228 discloses a long-life and high-output light emitting apparatus in which a solid-state light source is used.
In this light emitting apparatus, the small solid-state light source is connected to a light guide member such as an optical fiber, and the distal end portion of the light guide member is held by a holding member. A wavelength converting member such as a fluorescent material is provided at the distal end portion of the light guide member. A spacer is provided between the distal end portion of the light guide member and the wavelength converting member. This spacer has a through-hole portion. A metallic thin film which is a reflecting portion is provided on the circumferential surface of the through-hole portion. Some of the light emitted from the wavelength converting member functions as rearward emission light which is emitted from the wavelength converting member to the side of the light guide member.
The above-mentioned thin film reflects the rearward emission light toward the wavelength converting member so that the rearward emission light returns to the wavelength converting member. As a result, the rearward emission light is used as illumination light.
In Jpn. Pat. Appln. KOKAI Publication No. 2009-3228, the wavelength converting member covers the whole portion emission side opening portion of the spacer. This ensures that the light emitted from the light guide member enters the wavelength converting member. This also ensures that the rearward emission light is reflected by the thin film and enters the wavelength converting member again.
However, in general, the wavelength converting member has a scattering function to scatter some of wavelength-converted light having its wavelength converted by this wavelength converting member, or an absorption function to absorb the wavelength-converted light. Therefore, the light which is normally emitted to the outside is scattered by the wavelength converting member and absorbed by some other member. The light which is normally emitted to the outside is absorbed by the wavelength converting member. Accordingly, the amount of light is reduced. Thus, sufficient efficiency of light usage is not ensured.
The present invention has been made in view of these circumstances, and is intended to provide an illumination apparatus which can ensure sufficient efficiency of light usage.